Deadly outbreak of iron storage disease (ISD) in Italian birds of the family Turdidae

Abstract

A widespread deadly outbreak occurred in captive birds belonging to the family Turdidae in Italy. The present study was performed on 46 dead birds coming from 3 small decoy-bird breeders in central Italy. Only Turdus pilaris, Turdus iliacus, Turdus philomelos and Turdus merula were affected. No other species of bird held by these breeders died. A change of diet before the hunting season was reported from all breeders. Full necropsy of the animals and histological investigations of representative tissue samples were performed. Microscopical examination showed marked iron deposits in liver samples. Bacteriological investigations and molecular analysis to exclude bacterial and viral diseases were carried out. Contamination of food pellet samples by mycotoxins and analysis to detect heavy metal contaminants in food pellet samples were considered. An interesting result was the high iron content found in food pellets. It was higher than that considered suitable for birds, especially for species susceptible to development iron storage disease (ISD). Taken together, the results suggested an outbreak of ISD caused by the high iron content of food given to the birds before the hunting season. The high mortality recorded only in species belonging to the family Turdidae suggests a genetic predisposition in the affected birds.

Fig. 1.

Blackbird (Turdus merula). Liver with marked brown granular deposits consistent with hemosiderin localized especially in periportal hepatocytes (H-E, × 10).

Fig. 2.

Blackbird (Turdus merula). Panlobular storage of large dark blue material considered 257 to be iron deposits associated with severe hepatocytes sideronecrosis (Perls’ Prussian blue 258 staining, × 20).

Fig. 3.

Fieldfare (Turdus pilaris). Heart. Extensive myocardial necrosis characterized by 261 fragmented myocardial fibers and mucoid edema with scant leukocyte infiltration (H-E, × 20). 262